PURPOSE: To obtain at a low cost a method for controlling a switching process which suits each sort of printing press and operating conditions thereof, by comparing an angular position on each occasion with stored angular positions and by triggering the switching process assigned to the angular position, in the case when coincidence is found.

CONSTITUTION: On the occasion of starting a printing process, a program is started in a computer 30. In this program, an angular position inputted beforehand from a memory 39 to an operational memory of the computer is compared with angular positions of an increment transmitter 12. The minimum value of the angular positions stored is written in a register 36, and when a counter 34 reaches the same value, interruption of the program is triggered by a comparator 35. Therefore the computer puts a query as to which switching process belongs to this angular position, and gives corresponding data to an output unit 40. Next, the computer 30 inputs the angular position of the second smallest value to the register 36. The same operation continues hereinafter.